Yup, always thought La Punta an interesting option for a long layover. See the fortress, tour a submarine, maritime museum, don't wander into the depths of Callao but the tourist area ok. About 20 minutes by taxi, 10-12 soles.

Also for the shopper, there is an outlet mall beside the airport. Exit domestic arrivals side, walk to the road, turn left, less than 100 metres a nice new small mall with like 20 or more brand name outlet stores, restaurant etc.